Alkali alumino-silicate glasses are being used in applications where mechanical performance is important. These glasses can be formed using a fusion draw process. In a fusion draw process, liquid glass flows over one or more lips of a glass overflow trough and the liquid glass fuses at the bottom of the glass overflow trough to form a glass sheet. The glass overflow trough can be made from a forming block including an aluminum material. The size and quality of a glass sheet may be limited by physical properties of the glass overflow trough used to form the glass sheet. In addition, the lifetime of a glass overflow trough can be affected by its physical properties. Further improvement of refractory blocks used to make forming blocks and glass overflow troughs is desired.
The use of the same reference symbols in different drawings indicates similar or identical items.